• Electrical & Electronic Materials
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• v.17 no.5
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• pp.13-20
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• 2004

1996년 GaN와 near band edge emission(NBE) 및 yellow deep-defect level emission의 발광 기구가 ZnO의 greene mission과 매우 유사하다는 점이 발견된 이 후［1,2］, II-VIZnO반도체에 대한 광학적 성질에 많은 관심이 집중되기 시작하였다. 1960년대 C. Klingshirin［3］에 의해 bulk ZnO의 exciton luminescence가 관측된 이래로, 1980년대 후반부터 적층 박막 성장 법들이 급속도로 발전을 하여 오고 1988 S. Bethke등이 CVD로 성장한 ZnO의 NBE emission에 관심을 갖기 시작하였고［4］, 1996년 2K에서 GaN, ZnO사이의 유사한 발광기구가 알려졌고［5］, 도호쿠 및 일본 공업대에서 ZnO의 적층 성장 및 상온에서 defect에 기인한 emission이 없는 깨끗한 PL 의 관측, 상온 lasing, 육방정계 결정 구조에서 비롯된 6-fold symmetry PL 등이 보고되기 시작하였다. ［6-8］ 2000년에 들어서면서 MgO와 CdO와의 solid solution에 의한 밴드갭을 2.6-4.2 eV 까지 조절하는 가능성이 보고되었고 이를 이용한 ZnO/MgZnO MQW 구조에 대한 연구도 병행되었다.(중략)

• Applied Biological Chemistry
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• v.28 no.2
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• pp.56-61
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• 1985

The mass balances of calcium salts during the manufacturing processes of Tofu were established by conductometric method and chemical analysis method. During the manufacturing processes of soy milk and Tofu, 66% of solid and 63% of calcium was transfered from soy-bean to the soy milk, and 47.8% of total solid from soybean was transfered to the Tofu, respectively. When the $CaCl_2$ was used as coagulant, calcium contents in Tofu $(Y_{Tofu},\;mg{\cdot}Ca/g{\cdot}Tofu,\;wet\;basis)$ and drained solution $(Y_{drained\;soln},\;mg{\cdot}Ca/ml{\cdot}drained\;soln.)$ were linearly increased with the amounts of $CaCl_2(C,g{\cdot}CaCl_2/ml{\cdot}soy\;milk)$ added in soy milk, and correlative equations between them were obtained as $Y_{Tofu}=0.3369\;C+1.2689$ for Tofu$(moisture\;content:\;81.5{\pm}0.5%)$ with r=0.9898, and $Y_{drained\;soln}= 0.2899C+0.0399$ for drained solution with r= 0.9991. It was proved that conductometric method was reasonably applicable to the measurement of calcium contents of the products from every processes of Tofu manufacture except soy-bean. However the conductometric method was not recomendable in the case of $CaSO_4$ as coagulant due to its low solubility ana uneven distribution in soy milk and Tofu tissue.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 2000.06a
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• pp.179-193
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• 2000

Aluminium titanate (Al₂TiO5) with an excellent thermal shock resistant and a low the expansion coefficient was obtained by solid solution with MgO, SiO₂, and ZrO₂ in the Al₂TiO5 lattice or in the grain boundary solution through electrofusion in an arc furnace. However, these materials have low mechanical strength due to the presence of microcracks developed by a large difference in thermal expansion coefficients along crystallographic axes. Pure Al₂TiO5 tends to decompose into α-Al₂O₃ and TiO₂-rutile in the temperature range of 750-1300℃ that rendered it apparently useless for industrial applications. Several thermal shock tests were performed: Long therm thermal annealing test at 1100℃ for 100h; and water quenching from 950 to room temperature (RT). Cyclic thermal expansion coefficients up to 1500℃ before and after decomposition tests was also measured using a dilatometer, changes in the microstructure, thermal expansion coefficients, Young's modulus and strengths were determined. The role of microcracks in relation to thermal shock resistance and thermal expansion coefficient is discussed.

• Proceedings of the KAIS Fall Conference
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• 2001.05a
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• pp.40-46
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• 2001

The thermal stability of $Al_2TiO_{5}$ ceramics was improved by formation of solid solution with MgO, such as $MgAl_2O_4$ spinel through electrofusion in an arc furnance, and by limitation of grain size and microcracks with $SiO_2$, $ZrO_2$ and ${\alpha}$-$Al_2O_3$. The low thermal expansion properties of $Al_2TiO_{5}$ composites show the thermal hysteresis curves due to the strong anisotropy of $Al_2TiO_{5}$. These phenomena are explained by the opening and closing of microcracks. The relation between thermal hysteresis, microstructures and sintering temperature were studied by dilatometry.

• Environmental Analysis Health and Toxicology
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• v.14 no.4
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• pp.145-153
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• 1999

Effects of various concentrations of copper in solid fibrous form and methylglyoxal (MG) on phosphorus uptake and growth change of green algae Scenedesmus obliquus were studied. There was significant differences among cultures treated with various concentrations of copper and MG in growth of algae with parameters of cell numbers, photosynthetic rate and cellular morphology, and phosphorus uptake by cell. When the copper in media is treated with 25 mg or 50 mg per 100 ml of Bristol solution, the mean cell number of algae was 15.642${\times}$10$\^$6/ cells$.$ml$\^$-1/ and 12.986${\times}$10$\^$6/ cells$.$ml$\^$-1/, respectively, while those of algae in culture without copper was 18.486${\times}$10$\^$6/ cells$.$ml$\^$-1/. The mean cell area of 2450 ${\mu}$m$^2$, 1894 ${\mu}$m$^2$and 1697 ${\mu}$m$^2$in basic media, basic media with 25 mg of copper and basic media with 50 mg of copper was showed the inhibitory effect of copper on algal growth. The algal growth was stimulated by MG when the culture was treated with 25 mg of copper or without copper, while it was inhibited when the culture was treated with 50 mg of copper. It was considered that there was significant interaction between copper and MG on algal growth. The phosphorus concentration in algal medium treated with 25 mg or 50 mg of copper was 29.435 ppm and 26.224 ppm, respectively, while those of algae in culture without copper was 52.8 ppm, which shows that the application of copper in algal medium can prevent the availability of phosphorus to algal cell.

• Journal of Korean Society on Water Environment
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• v.24 no.6
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• pp.801-805
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• 2008

A fibrous material (p-phenylene-2,5-benzobisoxazole, PBO) was used as an adsorbent for solid phase extraction in order to simplify the extraction procedure. The extraction performance for di-(2-ethylhexyl) phthalate (DEHP) was examined with two types of PBO fibers (HM (High modulus) and AS (Regular type) types) by batch type sorption/desorption experiments. When 100 mg of the HM fibers were applied to 20 mL of the aqueous DEHP solution (less than $50{\mu}g/L$), more than 95% of DEHP was adsorbed on the fibers, however, the AS type fibers adsorbed alkyl phthalate up to 80%. In the case of $50{\mu}g/L$ of the initial concentration of DEHP, the adsorbed DEHP was extracted effectively with methanol and the maximum overall recovery ratio was 92.3%. The results indicated that the PBO fibers could be used as an adsorbent for alkyl phthalate analysis, and that the extraction procedure was not affected by suspended solids in a water sample.

• Korean Journal of Plant Resources
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• v.18 no.3
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• pp.456-461
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• 2005

This study was carried out to induce plant regeneration via shoot formation from sucker explants of Rubus fruticosus L. To induce adventitious shoots, sucker explants were sterilized in $1.2\%$ NaOCl solution, and cultured on the MS solid medium supplemented with kinetin (0.5, 1.0, 3.0 mg/L) and BA (0.5, 1.0, 3.0 mg/L), respectively. As above, to induce adventitious shoots, sucker explants were cultured on the MS solid medium supplemented with IBA (0, 0.1, 1.0 mg/L) and BA (0, 0.1, 1.0, 2.0 mg/L). After 4 weeks of culture, the highest frquency $(100\%)$ of shoot formation from sucker explants was obtained from the medium with 1.0 mg/L BA. The highest shoot number per explant from in vitro shoot explants was 5.3. After 10 weeks of culture, the number of shoot per explant was increased. The highest frequency $(85\%)$ of root formation was obtained at 0.5 mg/L glycine medium, when the explant with shoot were cultured on the MS medium containing glycine at various concentrations from 0 to 2.0 mg/L. The survival rate of the plantlets after transfer to plastic pots containing sand, soil, and vermiculite (1:1:1, vol.) was $95\%$. The results indicate that micropropagation procedure can be applied for an efficient mass propagation of Rubus fruticosus.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.8
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• pp.875-880
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• 2014

Recently, three-dimensional scaffolds and nanofibers are being developed for bone tissue regeneration. In this study, we fabricated a hybrid scaffold using a nano-micro precision deposition system. The fabrication process involved the application of the solid freeform fabrication (SFF) technology and electrospinning. The hybrid scaffolds were combined using micro scaffolds and nanofibers. The nanofibers were deposited on each layer of the micro scaffolding using the electrospinning process. The micro scaffolds were fabricated using the SFF technology at a temperature of $100^{\circ}C$, pressure of 650 kPa, and scan velocity of 250 mm/s. Nanofiber fabrication was conducted by means of electrospinning using the flow rate, solution concentration, distance from the tip to the collector (TCD), and voltage. The nanofibers were fabricated using a flow rate of 0.1 ml/min, voltage of 5 kV, TCD of 1 mm, and 10 wt% of solution concentration. MG-63 cells were seeded into the hybrid scaffold for the purpose of its evaluation.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2002.11a
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• pp.43-49
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• 2002

A7003 alloy has characteristics of their excellent weldability, high corrosion resistance and superior plastic working however the broadening of application for the alloy has been hampered by the lower extrudability associated by Mg content. For improvement of extrudability and enhanced recovery efficiency during Al scrap recyeling, it has been generally practiced to reduce Mg content in A7003 alloy. Therefore, it is necessary to investigate the influence of Mg content on mechanical strength and extrudability of A7003 alloy. For efficient material processing which has small amounts, life cycle assessment in material processing(MLCA) is evaluated. The quantitative analysis of energy requirements and $CO_2$ emission for production of A7003 extruded bar are estimated with different Mg content and billet pre-heating process (heating source by light oil or LPG). In particular, the estimation of energy requirements was performed within shipping and gating range (except the mining and extraction stages)to investigate the influence of the variables on energy requirements and $CO_2$ emission in detail. As Mg content increased, the flow stress and the extrusion pressure for A7003 alloy increased. It has been thought that an increment in extrusion pressure with increasing Mg content is caused by the solid solution hardening of Mg atoms in the matrix and increment in volume fraction of intermetallic compound, $Mg_2Si$. The extrudability and the tensile strength are equal to, or above that of conventional A 7003 alloy even the content of Mg varied from $1.1wt.\%\;to\;0.5wt.\%$ alloy. This means that minimizing the content of Mg in A7003 alloy can enhance recovery efficiency during Al scrap recycling. It can be quoted that rather than Mg content energy source for billet heating is a prime factor to determine the atmospheric $CO_2$ emission.

• Korean Journal of Materials Research
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• v.22 no.3
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• pp.111-117
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• 2012

The effect of Al addition on the precipitation behavior of a binary Mg-Zn alloy was investigated based on the changes in the morphology, distribution and element concentration of precipitates formed during aging treatment. The as-cast Mg-6.0 mass%Zn (Mg-6Zn) and Mg-6.0 mass%Zn-3.0 mass%Al (Al-added) were homogenized at 613 K for 48 h and at 673 K for 12 h; they were then solid solution treated at 673 K for 0.5 h and 1 h, respectively. The Mg-6Zn and Al-added alloys were aged at 403 K and 433 K. The peak hardness of the Al-added alloy was higher than that of the Mg-6Zn alloy at each aging temperature. Rod-like, plate-like, blocky, and lath-like precipitates were observed in the Al-added alloy aged at 433 K for 230.4 ks, although the rod-like and plate-like precipitates were observed in the TEM microstructure of the Mg-6Zn alloy aged at 433 K for 360 ks. Moreover, the precipitates in the Al-added alloy were refined and densely distributed compared with those in the Mg-6Zn alloy. The Cliff-Lorimer plots obtained by the EDS analysis of the rod-like ${\beta}_1^'$ and plate-like ${\beta}_2^'$ phases in the Al-added alloy peak aged at 433 K for 230.4 ks were examined. It was confirmed that the ${\beta}_2^'$ phases had higher concentration of solute Al atom than was present in the ${\beta}_1^'$ phases, indicating that the properties of precipitates can be changed by Al addition.